A method for determining the position of an object in a vehicle is known from EP 104 90 46. With that method, in particular the position of the head is determined by generating a differential image from two images taken successively by a camera, in which image only the contour of moving objects appears. The contours of the differential images are used to calculate the position of the head.
A method of determining the volume of objects located on the vehicle seat, such as a child car seat or an occupant, is also known. With an image recognition method of this type it is important to know the position and surface shape of the relevant vehicle seat in order, for example, to prevent confusing the head with the headrest or the upper body area with the backrest.